This invention relates to improvements in heat transfer units and more particularly to such heat transfer units as form a package for products which desirably are to be heated or cooled at the time of use. As here contemplated, each such unit will incorporate heat transfer means in an inactive state together with and normally separated from a liquid energizer, the intermixture of which in said heat transfer means will activate the same. The intermixture described is in this instance initiated by an axial compression of the container portion of the heat transfer package which forms its outer shell.
Certain disadvantages have attended the usage of prior art heat transfer units directed to the purpose described. These have stemmed, at least in part, from an inobviousness as to how and to what extent a control must be exerted to initiate the necessary heat transfer action. Rupturing and leakage at the joints has been a prevalent problem in squeeze type units of the type described. A more serious problem has been the difficulty in providing means to insure a rapid heat transfer effect such as required in an acceptable package. Difficulty has also been found in achieving proper structural requirements for a package of the type described. For such a package to be acceptable, it must be leak-proof, have adequate shelf life and be difficult to accidentally trigger while remaining susceptible of a simple and easy operation, as and when required.
In general a considerable number of heat transfer units as heretofore proposed have suffered problems of the type above noted, been limited as to their application, and their function has usually been less than satisfactory.